The government sought to step up pressure on Britain's "big six" energy suppliers to respond to concern that prices for residential customers are not falling fast enough. Alistair Darling said that the energy industry regulator, Ofgem ,would report every three months on what was happening to wholesale and retail prices.

However, wholesale prices have since fallen as the oil price has retreated from a record $147 (£97) a barrel to $50, but that has not fed through to household bills. Darling told the Commons: "I know there is concern that the fall in the price of wholesale energy has not been reflected quickly enough in household bills."

The average household bill has gone to between £1,200 and almost £1,300, causing mounting concern over the number of households living in fuel poverty.

There have been hints from some energy companies that, if the recent fall in wholesale prices is sustained, residential customers should start to benefit in the new year.

The industry argues that it shelters customers from sharp changes in prices, with increases and decreases in residential bills lagging changes in the wholesale market by several months.

Darling also used his report to warn the industry that he is prepared to bring in legislation if energy suppliers do not bring forward their own proposals to close what he described as "unfair gaps in pricing between payment methods".

An Ofgem inquiry found some customers paid more for pre-payment meters than could be justified by the cost of the service.